Shrub rose plant named ‘Morden Snowbeauty’

ABSTRACT

A new and distinct variety of shrub rose plant is provided which forms in clusters attractive semi-double somewhat flattened white blossoms. An open and semi-erect growth habit of excellent form is exhibited. The foliage is glossy dark green and contrasts nicely with the white blossoms. The plant propagates well by the use of softwood cuttings and possesses good winter hardiness. Petaloid stamens commonly are present. Excellent disease resistance particularly to blackspot its exhibited. It is particularly well suited for growing as an individual plant or as a mass planting to create ornamentation in the landscape.

SUMMARY OF THE INVENTION

The new variety of shrub rose plant (Rosa hybrida) of the presentinvention was created through a complex pedigree controlled breedingprogram that was carried out at Morden, Manitoba, Canada. The ‘AdelaideHoodless’ variety was crossed with Rosa arkansana Porter to obtain anoffspring that was crossed with the ‘Mount Shasta’ variety. This crossproduced a parent used in the creation of the new variety. The otherparent of the new variety was formed by the crossing of the ‘PrairiePrincess’ variety and the ‘Morden Amorette’ variety. None of the plantsused to create the new variety have been patented in the United States.The ‘Prairie Princess’ variety is a shrub rose (Rosa sp.) developed byG. Buck in 1972 and the ‘Mount Shasta’ variety is grandiflora rose (Rosasp.) developed by Swim and Weeks during 1963. The ‘Morden Amorette’variety and the ‘Adelaide Hoodless’ variety are members of the PARKLANDSeries of roses. Rosa arkansana Porter is a prairie hardy nativetetraploid rose found in the Great Plains region of North America. Thefinal cross of the breeding program was completed during 1984.

The parentage of the new variety can be summarized as follows:

[‘Prairie Princess’×‘Morden Amorette’]×[‘Mount Shasta’×(‘AdelaideHoodless’×Rosa arkansana Porter)].

It was found that a single plant of the new variety of shrub rose plantof the present invention was created through the above-identifiedbreeding program which possesses the following combination ofcharacteristics:

(a) exhibits an open and semi-erect growth habit,

(b) forms clusters of attractive semi-double somewhat flattened whiteblossoms,

(c) forms attractive glossy dark green foliage,

(b) propagates well by the use of softwood cuttings,

(e) exhibits good winter hardiness,

(f) exhibits excellent disease resistance, and

(g) is particularly well suited for growing as ornamentation in thelandscape.

Rose plants of the new variety can be grown well on their own rootsoutdoors without protection at Morden, Manitoba, Canada. Blossomproduction commonly begins in early June at Morden, Manitoba, Canada andcommonly is completed by mid-September. Good blossom coverage (e.g., upto approximately 30 percent or more of the entire plant at week three ofblooming) is achieved which contrasts nicely with the attractive darkgreen foliage.

Accordingly, the new variety well meets the needs of the horticulturalindustry. It can be grown to advantage as attractive ornamentation as anindividual plant or as a mass planting in parks, gardens, public areas,and residential landscapes.

The characteristics of the new variety have been found to be homogenousand stable and have been shown to be strictly transmissible by asexualpropagation by the rooting of softwood stem cuttings conducted atMorden, Manitoba, Canada.

The new variety initially was designated 84J3T403 and X6 andsubsequently has been named the ‘Morden Snowbeauty’, The name wasselected to reflect the white flower coloration and the excellent fieldperformance of the plant. It constitutes an attractive white-floweredmember of the PARKLAND Series of roses.

BRIEF DESCRIPTION OF THE PHOTOGRAPHS

The accompanying photographs show as nearly true as is reasonablypossible typical specimens of the plant, blossoms, and foliage of thenew variety. The plants were photographed during the summer whilegrowing in the landscape on their own roots at Morden, Manitoba, Canada.The plant age was approximately five years including the year requiredto root the cutting.

FIG. 1 illustrates a typical mature plant of the new variety. Thesemi-erect upright growth habit is shown.

FIG. 2 illustrates a cluster of typical white semi-double almost flatblossoms, as well as an unopened bud.

FIG. 3 illustrates typical foliage.

DETAILED DESCRIPTION

The chart used in the identification of colors is that of The RoyalHorticultural Society (R.H.S. Colour Chart). Common color terms are tobe accorded their ordinary dictionary significance. The description isbased on the observation of mature plants while growing on their ownroots outdoors in the landscape during the summer at Morden, Manitoba,Canada.

Class: Shrub.

Plant:

Height.—Approximately 31 to 96 cm. with a mean height of approximately74 cm. Juvenile cane growth is more arching and less erect thansubsequent growth. A fully mature plant commonly can assume a height ofapproximately 85 cm. The plant height and plant width vary considerablywith environmental conditions. Greater dimensions are produced withwarmer temperatures, greater precipitation, and with fertilization(primarily nitrogen).

Width.—Commonly approximately 46 to 128 cm. with a mean width ofapproximately 98 cm.

Habit.—Semi-erect, upright, and spreading.

Bark: Current season bark is Yellow-Green Group 144B and graduallychanges to Yellow-Green Group 144A on mature stems.

Thorns: Mature stems typically bear a sparse to moderate quantity ofreflexed prickles commonly having a length of approximately 3 to 7 mm.and an average length of approximately 5 mm. On the current seasongrowth smaller prickles commonly also are present. The coloration isGreyed-Purple Group 187B on young stems and Greyed-Purple Group 187A onmature stems older than one year.

Leaves: Compound and pinnate.

Leaflets.—Number: Commonly 3 to 9 with 7 leaflets being the most common.Configuration: Acute with a smoothly rounded base. Margins: Serrate.Size: Terminal leaflets commonly rante from approximately 2.1 to 7.5 cm.in length (mean approximately 5.9 cm.) and approximately 2.4 to 4.8 cm.in width (mean approximately 3.8 cm). General appearance: Dark green,and glossy. Petiolules: Very small and commonly <2 mm.

Color.—Adult foliage: Shiny dark green, Green Group 137A on the uppersurface and lighter dull green, Green Group 138B the under surface.Young stems: Yellow-Green Group 144A with a slightly reddish margin ofGreyed-Red Group 178A. Petioles: Green Group 137B, and possess adistinct groove.

Inflorescence:

Number of flowers.—Commonly in clusters of 3 to 10, and in clusters of 5on average. Peak flower cover has been observed in mid- to late-June.

Sepals.—Commonly 2 to 3 cm. in length, Green Group 143C on the outersurface and Yellow-Green Group 148D on the inner surface with atomentose inner surface.

Buds.—Shape: Acutely pointed. Color upon opening: Green-White Group157A.

Flower.—Shape: Tends to flatten when fully open as shown in thephotograph. The depth of the somewhat flattened flowers tends to beapproximately 2 cm. when fully open. Diameter: Commonly approximately 6to 12 cm., and 8 cm. on average. Color (when blooming): When fully openwhite as illustrated, White Group 155A on both surfaces. When onlypartially open slight pink tones sometimes are included in coolerweather. When fully mature, a slight petal edging of brown may bepresent. The base of the petals on the underside sometimes is paleyellow, near Yellow group 2C. Fragrance: Weak. Petal number: Commonlyapproximately 7 to 18. Petal configuration: Smooth and orbicular withrounded tips with reflexed outer edges. In many instances the midribscommonly are raised. Petal size: Commonly approximately 2.2. to 3.3 cm.in length (mean 2.8 cm.) and approximately 1.8 to 3.6 cm. in width (mean2.6 cm.). Stamens: Several petaloid stamens commonly are present havinga width of approximately 1 to 2 cm., the anthers produce fertile pollenand are medium yellow in coloration. Filaments: Commonly are nearlycompletely white. Peduncle: Commonly approximately 28 mm in length onaverage, moderate in strength, under heavy flower production may bendcausing a slightly drooping appearance, the coloration is Yellow-GreenGroup 144B, and a few small prickles sometimes are present. Pedicel:Similar in appearance to the peduncle, and commonly approximately ¾ thesize of the peduncle. Style: Yellow and of medium length. The stigmascommonly are exserted slightly. Receptacle: Round, Green Group 138B incoloration, and generally less than 2 cm. in diameter. Hips: Are formedeach season but commonly do not ripen fully under the specified growingconditions. Lasting quality: Long lasting approximately 7 to 14 days onthe plant and approximately 7 to 10 days when cut and placed in a vase.Warmer and drier conditions tend to shorten the bloom life on the plant.Petal drop: The petals detach well upon maturity with strong windstending to remove the older petals quickly.

Development:

Vegetation.—Good vigor.

Blossoming.—Commonly begins in early June on previous season buds andcontinues on current season growth until approximately the middle ofSeptember. The mean flower duration is 14 weeks. The percent coverage ofthe blossoms compares favorably to that of other roses of PARKLANDSeries and other white-flowered shrub roses under the specified growingconditions.

Hardiness.—Has survived in Agriculture Canada Hardiness Zone No. 2 withno protection. See Quellet and Sherk, Can. J. Plant Sci ., 47:3513-3518(1967). Some stem dieback may occur in severe winters, but regrowth isvery good.

Resistance to diseases.—Resistance is excellent to local populations ofblackspot (Diplocarpon rosae Wolf.), powdery mildew [Sphaerothecapannosa (Wallr, ex Fr.) Lev.], and rust (Phragmidium sp.).

Preferred mode of propagation.—The use of softwood cuttings to produceself-rooted plants is recommended. For instance, softwood cuttings of 1to 3 nodes in length can be taken during late spring through mid-summer,treated with rooting hormone (e.g., 3000 to 5000 ppm indole-butyricacid) and placed under intermittent mist or fog to achieve high rates ofpropagation which commonly exceed 85 percent. Tissue culture also can beused for propagation. Budded or grafted roses may suffer winter injuryat the specified growing location.

We claim:
 1. A new and distinct variety of shrub rose plantcharacterized by the following combination of characteristics: (a)exhibits an open and semi-erect growth habit, (b) forms in clustersattractive semi-double somewhat flattened white blossoms, (c) formsattractive glossy dark green foliage, (d) propagates well by the use ofsoftwood cuttings, (e) exhibits good winter hardiness, (f) exhibitsexcellent disease resistance, and (g) is particularly well suited forgrowing as ornamentation in the landscape; substantially as herein shownand described.